Acid producing plant



J. R. SHIELDS 2,942,953

ACID PRODUCING PLAN! Filed Oct; 14. 1955 June 28, 1960 IN VEN TOR. JemssE SHIELDS.

BY an,

s; 7- rozh/fi KS.

2,942,953 Patented June 28, 1 360 2,942,953 ACID PRODUCING PLANT JamesR. Shields, Penn Township, Pa., assignor to Elliott Company, Jeanette,Pa., a corporation of Pennsylvania Filed Oct. 14,1955, Ser. No. 540,490

3 Claims. (c1. 23-260) This invention relates to the manufacture ofacid, and more particularly to an improved plant or apparatus for makinga gaseous oxide that can be absorbed in water to make the acid.

For example,'the manufacture of nitric acid from ammonia involves thecatalytic oxidation of ammonia on a platinum catalyst, as is well known.The nitric oxide that is produced is absorbed in water to produce nitricacid. The rate of reaction and the final concentration of nitric acidare increased materially by increasing the reaction pressure levels.Accordingly, the practice has been to deliver a mixture of vaporizedammonia and compressed air to a reaction chamber where a platinumcatalyst causes the mixture to burn. This produces NO, some of whichbecomes N0 as it is cooled after leaving the reaction chamber. The gasis delivered to an absorption tower where the nitric oxide is absorbedin water to produce nitric acid. 'The top of the tower has an outlet forthe escape of excess nitrogen. It has been proposed to add heat to thisnitrogen in a combustion chamber so that it can be used to operate a gasturbine that helps to drive the air compressor, but in addition to thecost of operating the combustion chamber, the power thus recovered isstill insuflicient to make the compressor selfis that it requires aconsiderable amount of fuel to heat 7 the nitrogen in the combustionchamber high enough to operate the gas turbine efiiciently and toproduce steam in the waste heat boiler.

It is among the objects of this invention to provide an acid plant inwhich the air compressor is self-sustaining, without requiring either acombustion chamber to heat the tail gas from the absorption tower orsome other means of supplying power not generated by the heat of thechemical reaction.

In accordance with this invention an air compressor is driven by a gasturbine and a steam turbine. The substance that is used in the plant forproducing the necessary gaseous oxide is first vaporized or gasified, ifit is not already in that form, and mixed with compressed air and thenoxidized in a combustion chamber. Some of the heat of combustion is usedfor generating steam in a boiler connected with the inlet of the steamturbine. The outlet of the turbine is connected with a condenser whichin turn is connected by an economizer with the boiler. Gaseous oxidefrom the oxidation reaction is conducted through the economizer, whereit is cooled, and then to an absorption tower. Water is delivered to thetower to absorb the oxide and produce acid, which can be drained fromthe tower. The top of the tower is provided with an outlet for a tailgas and is connected with a heat exchanger that leads to the inlet ofthe gas turbine. The heat exchanger also is exposed to the heat ofcombustion in order to raise the temperature of the tail gas to thedesired point before it reaches the gas turbine. The power produced inthis way by the two turbines together is sufficient to drive thecompressor.

' The preferred embodiment of the invention is illustrated in theaccompanying drawing, which is a diagrammatic view of my acid makingplant.

Referring to the drawings, a low-pressure compressor 1 and ahigh-pressure compressor 2, or equivalent low and high-pressure stagesof a single compressor, are connected through the cooling side of anintercooler. Where the substance to be oxidized must first be vaporized,this unit may be a combination intercooler and vaporizer 3. The outletof the high-pressure compressor is connected by a conduit 4 with anotherconduit 5 leading from the vaporizing side of the -vaporizer-intercoolerto the inlet of a reaction or combustion chamber inside a pressurecasing 7. A liquid substance to be converted into a gaseous oxide inthis plant, such as ammonia, is delivered by a pump 8 to thevaporizer-intercooler, where it is vaporized by the heat extracted by itfrom the compressed air, which is thereby cooled. The compressors aredriven by gas turbine 9 and a steam turbine 10.

As the mixture of vapor and compressed air enters one end of thecombustion chamber, it burns and produces considerable heat. Thisoxidation reaction also produces the gaseous oxide that is absorbed bywater later in the plant, to form an acid. In making nitric acid,vaporized ammonia is oxidized with the compressed air as the mixture ofair and vapor pass over a platinum catalyst 12, generally in the form offine gauze, in the combustion chamber. The reaction produces NO and N0the N0 being formed principally as the gas is cooled. The gas leavesthe'other end of the chamber through a conduit 13 and then flows throughan economizer 14 and another conduit 15 and into the lower part of anabsorption tower 16, to the top of which water is delivered through apipe 17in order to form nitric acid that can be drained out of 'thebottom of the tower.

The nitrogen tail gas from the tower escapes through an outlet in itsupper end and flows through a conduit 18 to a heat exchanger 19 locatedin combustion chamber casing 7. The outlet of the exchanger is connectedby a conduit 20 with the inlet of the gas turbine. It will be seen thatthe heat generated in the chamber by the burning of -the air and ammoniavapor mixture will heat the gas in the heat exchanger.

The power obtained from the gas turbine is not sufiicient to drive thecompressors. It is necessary to add to it the power of the steam turbine10. The steam for this turbine is produced by a boiler located in thereaction chamber and connected by a steam pipe 22 with the turbineinlet. The boiler heat transfer surfaces absorb heat released bycombustion over catalyst 12 and protect the pressure casing 7 of thecombustion chamber against excessive temperatures. The boiler hasprimary and secondary evaporators 23 and 24, respectively, that mostsuitably are so arranged that the hot gaseous oxide flowing through thechamber will first heat the primary evaporator, then the heat exchanger19 and finally the secondary evaporator. With this arrangement, whereinprimary evaporator 23 controls the gas temperatures to heat exchanger19, the nitrogen gas in the heat exchanger will not be overheated, andyet will be heated to a high enough temperature, preferably, about 1000F. to 1100 F., for eflicient operation of the gas turbine. The secondaryevaporator then further reduces the temperature of the gaseous oxide toa value where it can be brought down to about 250 F. by the economizer14. As members 12, 23, 19 and 24 are all in a single pressure casing 7,instead of in separate units piped together, the boiler and heat -fromthe gas from the combustion chamber.

exchanger can recover as much heat as desired from catalyst 12.

The outlet of the steamturbine leads to a condenser 26 which isconnected by a pipe 27 to the economizer. In the economizer the water isheated by heat extracted The; hot water outlet of the economizer-isconnected by a'pipe 28 to the secondary evaporator 24.

The steam produced by the boiler drives the, steam turbine to produceenough power in conjunction withthe gas turbine to operate thecompressors. In most cases, there will be a surplus of power which canbe used. for driving an electric generator-29 connectedwith thetur-.bines. Also, in some instances it may be desirable, toadd :a waste heatboiler or a superheater for evaporator 23 to recover additional heat.from the gas turbine exhaust gases.

Other acids may be made in this; same general way from such substances,as sulfur, phosphorous, methane and the like which can be converted intogaseous oxides in this plant.

According to the provisions of, the patent statutes, I

have explained the principle of my invention and have illustrated anddescribed what I now consider to represent its best embodiment. However,I desire to have it understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallyillustrated and described.

- Iclaim:

1. A plant for making acid by absorbing in water a evaporatorsconnec'ted with the inlet of, the steam, turbine and heated by the heatof said combustion, a condenser connected with the steam turbine outlet,an economizer connecting the condenser with the boiler, an absorptiontower, means for conducting said gaseous oxide through the economizer tosaid, tower, means for delivering water to the tower to absorb saidoxide and produce said acid therein, the top of the tower being providedwith a tail gas outlet, and a heat exchanger connecting said tower:outlet with the inlet of the gas turbine, the exchanger being exposedto said heat of combustion betweenthe evaporators for raising thetemperature of the tail gas before it reaches the gas turbine.

2. A plant for making acid by absorbing in water a gaseous oxideproductive of said acid and produced by oxidation of a'substanceproductive of said oxide with compressed air, said plant comprising highand low pressure compressors for air, a gas turbine and a steam turbinefor driving the compressors, a vaporizer-intercooler between thecompressors, means for conducting said substance in liquid phase to thevaporiZer-intercooler to vaporize it as it cools the partiallycompressed air, means for mixing said vapor andcompressed air from thehigh pressure compressor, a combustion chamber for burning said mixtureto produce said gaseous oxide, a conduit delivering 'said'mixture to.said chamber, a: boiler having primary and secondary evaporatorsconnected with the inlet of the steam turbine and heated by the heat ofsaid combustion, a condenser connected with the steam turbine outlet, aneconomizer connecting the condenser with the boiler, an absorptiontower, means for conducting said gaseous oxide through the economizer tosaid tower, means for delivering water to the tower to absorb said oxideand produce said acid therein, the top of the tower being provided witha tail gas outlet, and a heat exchanger connecting said tower outletwith the inlet'of the gas turbine, the exchanger being exposed to saidheat of combustion between the evaporators for raising the temperatureof the tail gas before it reaches the gas turbine.

3. A plant for making acid by absorbing in water a gaseous oxideproductive of said acid and produced by oxidation of a substanceproductive of said oxide with compressed air, said plant comprising anair compressor, a gas turbine and a steam turbine for driving thecompressor, a casing containing a combustion chamber for producing saidoxidation, a conduit connecting the outlet of the compressor with, saidcasing, a boiler in. said combustion chamber casing having primary andsecondary evaporatorsjconnected' with the inlet, of the steam turbine, acondenser connected with the steam turbine outlet, an economizerconnecting. the condenser with the boiler, an absorption tower,- meansfor conducting said gaseous oxide through the economizer to said tower,means for deliver- ,ing water to the tower to absorb said oxide andproduce said, acid therein, the top of the tower being provided with atail gas outlet, and a heat exchanger in said combustion chamber casingbetween the evaporators and connecting said tower outlet with the inletof the gas turbine, the exchanger being, adaptedto raise the temperatureof, the tail gas before it reaches the gas turbine.

References Cited in the file of this patent UNITED STATES PATENTS2,135,733 Richardson Nov. 8, 1938

1. A PLANT FOR MAKING ACID BY ADSORBING IN WATER A GASEOUS OXIDEPRODUCTIVE OF SAID ACID AND PRODUCED BY OXIDATION OF A SUBSTANCEPRODUCTIVE OF SAID OXIDE WITH COMPRESSED AIR, SAID PLANT COMPRISING ANAIR COMPRESSOR A GAS TURBINE AND A TREAM TURBINE FOR DRIVING THECOMPRESSOR, A COMBUSTION CHAMBER FOR PRODUCING SAID OXIDTION, A CONDUITCONNECTING THE OUTLET OF THE COMPRESSOR WITH SAID CHAMBER, A BOILERHAVING PRIMARY AND SECONDARY EVAPORATORS CONNECTED WITH THE INLET OF THESTREAM TURBINE AND HEATED BY THE HEAT OF SAID COMBUSTION, A CONDENSERCONNECTED WITH THE STEAM TURBINE OUTLET, AN ECONOMIZER CONNECTING THECONDENSER WITH THE BOILER, AN ADSORPTION TOWER, MEANS FOR CONDUCTINGSAID GASEOUS OXIDE THROUGH